1. Field of the Invention
The present invention relates to a process for producing aromatic compounds, and specifically, it relates to a process for producing another aromatic compound from an aromatic compound by oxidation using molecular oxygen. More specifically, it relates to a process of subjecting an aromatic compound to direct oxidation using molecular oxygen to thereby produce a corresponding aromatic hydroxy compound; a process of subjecting an aromatic compound to oxidative coupling to thereby produce a corresponding aromatic compound including plural moieties of the aromatic compound directly combined with each other through a single bond; and a process of subjecting an aromatic compound to oxidative coupling with an olefin or an acetylene to thereby produce a corresponding aromatic compound having an alkenyl group or an alkynyl group. Such aromatic hydroxy compounds are useful as, for example, organic chemical materials, pharmaceutical materials, agrochemical materials, and polymer materials. The aromatic compounds each including plural moieties of an aromatic compound directly combined with each other through a single bond are useful as heat transfer media, raw materials in organic syntheses, dyes, and pharmaceutical materials. The aromatic compounds each having an alkenyl group or alkynyl group, such as stilbene, derivatives thereof, cinnamic acid, and derivatives thereof, are useful as polymer materials, dyes, synthetic intermediates for pharmaceuticals and other fine chemicals, and intermediate materials for other organic chemical products.
2. Description of the Related Art
Phenol has been industrially produced by a process comprising the steps of oxidizing cumene to yield cumene hydroperoxide and decomposing cumene hydroperoxide in the presence of an inorganic acid. In contrast, a process has been proposed to produce phenol by direct oxidation of benzene. However, this process requires high temperature and high pressure conditions, and demands have been made on processes for producing phenols under milder conditions.
An oxidative coupling reaction of an aromatic compound such as benzene using oxygen as an oxidizing agent is an ideal preparation process of aromatic ring assembly compounds with less burden on the environment and with high atom efficiency. This process generally uses a palladium compound as a catalyst, but its catalytic efficiency is not always sufficiently high.
An attempt has been made to produce a corresponding aromatic compound having an alkenyl group by oxidative coupling between an aromatic hydrocarbon and an olefin in the presence of a catalyst. This reaction enables activation of a carbon-hydrogen bond of the aromatic hydrocarbon by action of the catalyst to thereby form a novel carbon-carbon bond and becomes a focus of attention as an ideal reaction with high atom efficiency. For example, Acc, Chem. Res., 34, 633(2001) reports an oxidative coupling reaction between an arene and an alkene by catalysis of a palladium compound using benzoquinone/t-butyl hydroperoxide as a reoxidant. However, this process must use peroxides having low handleability.